1. Field of the Invention
The invention concerns a firing device for a plurality of electric valves, especially thyristors, with each of whose control paths a firing circuit with a detector for electromagnetic radiation is associated with a transmitter which is controlled by a firing control signal and is equipped with a radiator which energizes the individual detectors. The detectors are arranged close together in a plane perpendicular to the direction of radiation of the radiator.
2. Description of the Prior Art
A firing circuit which derives firing energy from the voltage at the anode-cathode path of the respective valve is well known (German Pat. No. 1,538,099) to use for firing an electric valve, particularly a thyristor. In this connection, a pulse capacitor is used which is charged by this voltage and is discharged, when needed, by means of a switching element onto the control path of the valve. As the switching member, in particular, a light-controlled thyristor is used which can be triggered through light irradiation from a light source placed at some distance. In this manner, electric potential differences which exist between the light source, as the transmitter of electromagnetic radiation, and the electric valve, have no influence on the firing. Such a firing circuit is therefore used preferably for the firing of electric valves for high voltage, particularly of high-voltage thyristors which are employed in a rectifier arrangement.
Another possibility of transmitting a firing control signal by radiation from a transmitter to a firing circuit which is equipped with a detector for this electromagnetic circuit, is described in Swiss Pat. No. 413,993. High frequency radiation is used here as the electromagnetic radiation. The firing of one or several valves by means of a high-frequency transmission path is largely free of interference and is particularly well suited for the firing of thyristors which are used in rectifiers for high-voltage d-c transmission systems.
It is known (German Offenlegungsschrift No. 1,513,868) to arrange the individual detectors in a circle around the transmitter as the center. It is also known (German Offenlegungsschrift No. 2,026,901) that a spherical configuration can be used as well. So that all detectors are subjected to the same radiation intensity, they must be arranged at the same distance from the radiator. This requirement is a considerable limitation of the possibilities to place the detectors.
It is an object of the present invention to arrange, in the firing device described above, the detectors in a space-saving manner and with freedom of placement, as far as their distance from the radiator is concerned, where every detector is to be irradiated with approximately the same radiation intensity, so that overall, the power and the radiating surface area of the transmitter can be kept small.